Priority is claimed to Patent Application Number 2001-80907 filed in Republic of Korea on Dec. 18, 2001, herein incorporated by reference.
1. Field of the Invention
The present invention relates to a method of forming a floating dome structure lifting up from the surface of a substrate and a method of manufacturing a field emission device (FED) employing the floating dome structure.
2. Description of the Related Art
Manufacturing field emission device includes a series of semiconductor processes, i.e., formation of a cathode electrode, formation of a gate insulation layer, and formation of a gate electrode. In addition, photolithography and dry or wet etching are performed on a substrate from the gate electrode to the top of the cathode electrode to form a gate hole so that the top of the cathode electrode below the gate electrode can be exposed through the gate hole. Then, an emitter, for example, a micro tip or a carbon nano tube (CNT), is formed on the bottom of the gate hole, i.e., on the exposed top surface of the cathode electrode.
FIGS. 1 and 2 are schematic sectional views of basic structures of general FEDs employing CNTs as electron emitters. FIG. 3 is a schematic sectional view of an FED employing micro tips as electron emitters, specifically provided with a vacuum bridge focusing structure, as disclosed in U.S. Pat. No. 6,137,213. For clarity of description, the same reference numerals denote the same elements having the same functions in FIGS. 1 through 3.
Referring to FIGS. 1 and 2, a cathode 2 is formed on the top of a substrate 1, and CNTs 3 are formed on the cathode 2. A gate insulation layer 5 and a gate electrode 6 are formed on the top of the substrate 1 to provide a gate hole (or a gate well 4 or 4xe2x80x2), in which the cathode 2 and the CNTs 3 are located. The gate hole 4 of FIG. 1 has the shape of a pot, and the gate hole 4xe2x80x2 of FIG. 2 has a vertical cylindrical shape. This difference is caused by the type of etching method. The gate hole 4 of FIG. 1 is formed by a wet etching method, and the gate hole 4xe2x80x2 of FIG. 2 is formed by a dry etching method.
In the above-mentioned structure, the thickness of the gate insulation layer 5 depends on the distance between the CNTs 3 and electrons emitted and moving away from the CNTs 3. The distance between the CNTs 3 and electrons must be over a predetermined distance in order to smoothly enable electrons to be emitted and smoothly control and accelerate the electrons. Accordingly, the gate insulation layer 5 must have a sufficient thickness to secure the distance mentioned above. However, a single layer has a limitation in thickness, and manufacturing costs increase in relation to the increase of the thickness.
To overcome these problems, the FED of FIG. 3 employing vacuum bridge focusing electrodes 7, in addition to the above-described elements, has been proposed. Since it is difficult to form electron emitters using CNTs, conventional micro tips 3xe2x80x2 are used as electron emitters. Since formation of a photoresist layer, deposition of a metal layer, and patterning are required to form the focusing electrodes 7 in manufacturing the FED of FIG. 3, manufacturing is complicated and time consuming. A complicated structure as shown in FIG. 3 is vulnerable to residual stress of an internal structure and easily deforms. Moreover, it is difficult to manufacture uniform electrodes to have uniform potential in controlling a sub pixel, i.e., a group of multiple micro tips. (see U.S. Pat. Nos. 5,973,444 and 6,137,213)
To solve the above-described problems, it is an object of the present invention to provide a method of easily forming a floating dome structure, such as applying a focusing electrode to a field emission device, lifting up from a substrate and a method of manufacturing an FED employing the floating dome structure.
To achieve the object of the present invention, there is provided a method of forming a predetermined stack structure, which is formed on a substrate, into a floating structure. The method includes forming an expansion causer layer, which can generate a byproduct from the reacting with a predetermined reactant gas causing volume expansion, on the substrate; forming an object material layer for the floating structure on a resultant stack; forming a hole through which the reactant gas is supplied on a resultant stack; supplying the reactant gas through the hole so that the object material layer partially lifts up from the substrate due to the byproduct generated from the reaction of the expansion causer layer with the reactant gas; and removing the byproduct through the hole so that the portion of the object material layer lifting up from the substrate can be completely separated from the substrate to form the floating structure.
In other words, unlike conventional methods of forming a sacrificial layer having a thickness corresponding to the height of a floating structure and forming a floating structure to have a desired shape at an initial stage, the present invention employs a technique of simply depositing a material layer or layers and allowing the material layer or layers to be transformed to have a desired shape by the generation and expansion of an outgrowth from an underlying layer so that various types of inventions can be derived from the present invention.
Accordingly, to achieve the object of the present invention, in one embodiment, there is provided a method of forming a dome-shaped structure lifting up from a substrate. The method includes forming a metal catalytic layer on the substrate; forming an amorphous material on the metal catalytic layer, the amorphous material having an opening portion that partially exposes the metal catalytic layer; supplying hydrogen gas and carbon oxide gas through the opening portion while heating the substrate so that a carbon layer grows between the amorphous material and the metal catalytic layer surrounding the opening portion to form a predetermined carbon layer and force the amorphous material to lift up from the substrate; and removing the carbon layer through the opening portion so that the amorphous material around the opening portion is partially separated from and floats over the substrate.
Preferably, the metal catalytic layer is a Nixe2x80x94Fexe2x80x94Co alloy, and the amorphous material is amorphous silicon.
Preferably, the catalytic metal layer is formed by a deposition method, and the amorphous material layer or amorphous silicon layer is formed by a chemical vapor deposition (CVD) method. In addition, it is preferable that the carbon oxide and the hydrogen gas are supplied during a CVD process.
In another embodiment, there is provided a method of manufacturing a gate electrode having a floating structure lifting up from a substrate in a field emission device. The method includes forming a cathode on the substrate; forming a catalytic metal layer on the top of the cathode; forming an amorphous material layer having a predetermined thickness on a resultant stack; forming a gate electrode on the top of the amorphous material layer; vertically forming a hole in a resultant stack to partially expose the surface of one of the catalytic metal layer and the cathode; supplying hydrogen gas and carbon oxide gas through the hole while heating the substrate so that a carbon layer is grown between the amorphous material layer and its underlying stack around the hole and forces the amorphous material layer to lift up from the substrate; and removing the carbon layer through the hole so that the amorphous material layer and the gate electrode around the hole are partially separated from and float over the substrate.
Preferably, the method also includes forming an insulation layer on the cathode to a predetermined thickness before the step of forming the catalytic metal layer. The insulation layer includes an opening portion which corresponds to the hole, and more preferably, is coaxial with the hole.
In still another embodiment, there is provided a method of manufacturing a gate electrode having a floating structure lifting up from a substrate in a field emission device. The method includes forming a cathode on the substrate; forming a gate insulation layer on the cathode to a predetermined thickness; forming a gate electrode on the gate insulation layer; forming an upper insulation layer having an opening portion on the gate electrode to a predetermined thickness; forming a catalytic layer on the top of the gate electrode exposed at the bottom of the opening portion of the upper insulation layer; forming an amorphous material layer on a resultant stack to a predetermined thickness; forming a second gate electrode on the amorphous material layer; forming a hole corresponding to the opening portion from the top of the second gage electrode to directly below exposing the surface of either the catalytic layer or the cathode; supplying hydrogen gas and carbon oxide gas through the hole while heating the substrate so that a carbon layer is grown between the amorphous material layer and its underlying stack surrounding the hole and forces the amorphous material layer to lift up from the substrate; and removing the carbon layer through the hole so that the amorphous material layer and the second gate electrode around the hole are partially separated from and float over the substrate.
In still another embodiment, there is provided a method of manufacturing an FED including a gate electrode having a floating structure. The method includes the steps of forming a cathode on a substrate; forming a gate insulation layer on the cathode to a predetermined thickness; forming a gate electrode on the gate insulation layer; forming an upper insulation layer having an opening portion on the gate electrode to a predetermined thickness; forming a catalytic layer on the top of the gate electrode exposed at the bottom of the opening portion of the upper gate insulation layer; forming an amorphous material layer on a resultant stack to a predetermined thickness; forming a second gate electrode on the amorphous material layer; forming a hole corresponding to the opening portion from directly below to the top of the second gage electrode and expose the surface of one of the catalytic layer and the cathode; supplying hydrogen gas and carbon dioxide gas through the hole while heating the substrate so that a carbon layer grows between the amorphous material layer and its underlying stack around the hole and makes it so that the amorphous material layer lifts up from the substrate; removing the carbon layer through the hole so that the amorphous material layer and the second gate electrode around the hole are partially separated from and float over the substrate; supplying a photoresist into the hole and on the second gate electrode to fill the hole with the photoresist and form a photoresist film on the second gate electrode to a predetermined thickness; removing the photoresist from the hole; growing a catalytic material on the top portion of the cathode, which is exposed at the bottom of the hole, to form a catalytic layer for growing carbon nano tubes (CNTs); depositing a CNT component material on the entire surface of a resultant stack to form a CNT array on the catalytic layer at the bottom of the hole; and removing the photoresist from a portion around the hole in a resultant stack and from the second gate electrode so that unnecessary components including the catalytic material are removed.